In this Phase II STTR application, we will build upon work conducted in our successful Phase I project which established the technical merit, acceptability and feasibility of developing a Web-based intervention, MyFAP.org, for adolescents and young adults (AYAs) with familial adenomatous polyposis (FAP). The main research goal of Phase II is to evaluate the efficacy of MyFAP.org in improving knowledge, self-efficacy, and quality of life-related outcomes among AYAs with FAP in a randomized controlled trial. Research Design and Methods. In Phase II, we propose to complete the development of the MyFAP.org intervention, including both content and technical enhancements. We will evaluate the efficacy of MyFAP.org in improving knowledge, self-efficacy, and related domains in a randomized trial of young persons with FAP. This Phase II project will result in a final product that is effective in providing support and facilitating self-management and coping with the medical and psychological demands of FAP, and will serve as a model for delivering web-based intervention content to other populations that suffer from rare conditions. A total of 130 AYAs will be randomized to the MyFAP.org intervention arm or an attention control arm consisting of a Web site with information on healthy lifestyle behaviors. Participants will complete baseline assessments, then will be provided with a hyperlink to access either MyFAP.org or the healthy lifestyle behavior website. Follow- up assessments will be conducted at one- and three-months post-intervention. PUBLIC HEALTH RELEVANCE: Familial adenomatous polyposis is an inherited cancer syndrome that is characterized by the development of hundreds of polyps, usually beginning by puberty, and by a nearly a 100 percent lifetime risk of colorectal cancer unless medical intervention is undertaken. To prevent cancer, affected persons are advised to begin screening by endoscopy beginning in their adolescent years, and will need to consider having a prophylactic colectomy by their late teens or early twenties. Despite the significant medical and psychological burden of FAP on adolescents and young adults, scant informational and supportive resources exist for this group. Our long- term goal is to develop and evaluate an intervention that will provide information and support to facilitate young persons' self-management and coping with the unique medical and psychological demands of FAP.